Rail carriage group

ABSTRACT

A rail carriage group ( 1 ) for a crane ( 3 ), in particular a gantry crane, which is moveable on rails ( 2 ) with a rectilinear rail profile and around at least one curve and in a transition between the rectilinear rail profile and the curve, with at least two, in particular at least four, running wheels ( 4 ), the running wheels ( 4 ) supporting subframes ( 5 ) of the rail carriage group ( 1 ), and the subframes ( 5 ) supporting a superstructure ( 6 ) of the rail carriage group ( 1 ), wherein at least one of the running wheels ( 4 ), preferably each running wheel ( 4 ), is rotatable individually about a running-wheel axis of rotation ( 7 ) which is vertical in the operating position.

BACKGROUND

The present invention relates to a rail carriage group for a crane, in particular a gantry crane, which is moveable on rails with a rectilinear rail profile and around at least one curve and in the transition between the rectilinear rail profile and the curve, with at least two, in particular at least four, running wheels, the running wheels supporting subframes of the rail carriage group, and the subframes supporting a superstructure of the rail carriage group. Furthermore, the invention also relates to a crane, in particular a gantry crane, with at least one rail carriage group according to the invention.

Rail carriage groups for gantry cranes are basically known. One exemplary embodiment of a rail carriage group is described in EP 1 911 716 B1. However, this document does not discuss the problem of how a rail carriage group for cranes, in particular for gantry cranes, should be designed when the crane has to move rectilinearly and around at least one curve in the rails. Nowadays, frequently because of the constricted space conditions which are provided in situ and which no longer permit the rails on which the crane or gantry crane is intended to travel to be laid exclusively rectilinearly, the rails on which the crane or gantry crane is moved also have to be guided around a curve. It is already known from EP 1 911 716 B1 to install a joint which is also rotatable about a vertical axis when the superstructure of the rail carriage group is connected to an end carriage of the crane. However, this is not used in EP 1 911 716 B1 for traveling around a curve.

If the crane or gantry crane is intended also to be able to travel around a curve, the prior art, which is known from obvious prior use, generally makes provision for connecting two or more running wheels, apart from the running-wheel axis of rotation thereof, rigidly in at least one subframe and to realize the curve-traveling capability of a corresponding possibility of rotation about a vertical axis between the subframe and the superstructure or in the superstructure.

It has been shown in practice that, in the case of the solutions known in the prior art, a relatively high degree of wear occurs on the running wheels and also on the rails because of the large loads of often several hundred tonnes.

SUMMARY

It is the object of the invention to improve a rail carriage group of the type in question to the effect that it permits as low-wearing travel as possible on the rail rectilinearly and around at least one curve and in a transition in-between.

This is achieved according to the invention by at least one of the running wheels, preferably each running wheel, being rotatable individually about a running-wheel axis of rotation which is vertical in the operating position.

A central concept of the invention is therefore to develop the rail carriage group to the effect that at least one of the running wheels, preferably each running wheel, can be rotated individually about the vertical running-wheel axis of rotation and therefore, in the case of rail sections running rectilinearly and also in the case of traveling around curves, each running wheel can adopt the optimum position relative to the rail at each point of the curve. This applies especially to the transitions between a rectilinear rail profile and a curved rail profile, i.e. a curve, and vice versa. Due to the optimum position of the running wheels on the rails in each section of the rail, i.e. rectilinearly and in a curve, the abrasion and wear on the running wheels and also on the rail are minimized. A further important advantage of the design according to the invention of the rail carriage group is provided in that the latter can also travel around comparatively tight curves with comparatively small curve radii.

For this purpose, in particularly preferred embodiments of the invention, at least one of the running wheels, preferably each running wheel, is assigned a dedicated subframe, and the subframe is rotatable together with the running wheel about the running-wheel axis of rotation which is vertical in the operating position.

Generally speaking, a subframe is the supporting element in which the running wheel is mounted rotatably about the running-wheel rotational axis thereof, which runs horizontally in the operating position, for rolling along the rail. The operating position is that position in which the rail carriage group or the crane is located with the running wheels thereof on the rail or the rails and can be moved along the rails. In most cases, provision is made for the rail carriage group to have more than two running wheels. The number of running wheels per rail carriage group is generally an integral multiple of the number two. Customarily, a rail carriage group runs with all of the running wheels thereof on precisely one rail. The horizontal running-wheel rotational axis, about which the respective running wheel rotates in the operating position when rolling on the rail, and the running-wheel axis of rotation which is vertical in the operating position and about which the running wheel is rotatable for traveling around a curve, can basically be arranged in such a manner that they intersect, preferably at a right angle. However, in preferred embodiments, the running wheels for rolling along the rail are in each case rotatable about a running-wheel rotational axis which is horizontal in the operating position, and, preferably in each case, the running-wheel rotational axis of the running wheel and the running-wheel axis of rotation of the running wheel are arranged skew with respect to each other. The word “skew” here should be understood in the mathematical sense. It therefore means that the straight lines running through the running wheel rotational axis and the running-wheel axis of rotation do not intersect anywhere in space and are also not parallel to each other. However, in these skew embodiments, provision is advantageously made for a parallel to the running-wheel rotational axis of the running wheel to exist, said parallel intersecting the running-wheel axis of rotation of the running wheel at a right angle, and vice versa.

In order to be able to realize the rotatability of the running wheels about the running-wheel axis of rotation thereof, which is vertical in each case, with a smaller number of required joints, in particularly preferred embodiments of the invention in each case two of the running wheels and/or two of the subframes are rotatable about a common running-wheel axis of rotation which is vertical in the operating position.

This is possible in particular in the case of an skew arrangement of running-wheel rotational axis and running-wheel axis of rotation.

In particularly preferred embodiments of the invention, the running wheels of the rail carriage group are the sole components of the rail carriage group that introduce the load produced by the rail carriage group itself and generated by the load on the rail carriage group into the rails. Therefore, in these preferred alternatives, the running wheels of the rail carriage group jointly transmit the entire load, which, in the operating position, emanates in the vertical direction from the rail carriage group itself and rests on the rail carriage group, to the rail. By this means, all of the other components of the rail carriage group that are in direct contact with the rail are freed from the load and are therefore subject to significantly less risk of abrasion.

As already explained at the beginning, the invention not only relates to a rail carriage group per se, but also to a crane, in particular a gantry crane, wherein said crane has at least one rail carriage group according to the invention, preferably three or four rail carriage groups according to the invention. In particular in the case of gantry cranes, provision is preferably made for said gantry cranes to have one rail carriage group according to the invention per vertical support in order to permit rectilinear travel and travel around a curve on the rails.

With regard to the designation of the diverse axes of rotation or rotational axes as being vertical or horizontal and also the terms vertically and horizontally also being referred to in other ways, it is pointed out that this is generally correct only when the running surfaces of the rails on which the running wheels roll run exactly horizontally. In practice, there are deviations therefrom of generally a few degrees. If the running surfaces of the rails are not exactly horizontal, then, as a rule, the axes of rotation or rotational axes referred to are also no longer oriented exactly vertically or horizontally. Here, however, for linguistic simplification, axes of rotation which are not exactly vertical are also referred to as being vertical and rotational axes not running exactly horizontally are also referred to as being horizontal. The same applies to other uses of the words vertically and horizontally. The angular deviations from the exactly vertical or exactly horizontal profile, in particular of the axes of rotation and rotational axes, generally, however, smaller than/equal to 10° in any case. Within this context, it would also be possible to refer to substantially vertically or substantially horizontally.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and details of preferred embodiments of the invention are explained by way of example below with reference to the description of the figures, in which:

FIG. 1 shows an example of a gantry crane designed according to the invention, in a schematically reduced illustration;

FIGS. 2 and 3 show examples of how rails can be laid, on which rail carriage groups according to the invention can be moved;

FIGS. 4 to 6 show illustrations for a first exemplary embodiment of a rail carriage group according to the invention;

FIGS. 7 to 9 show illustrations for a second exemplary embodiment of a rail carriage group according to the invention;

FIGS. 10 to 12 show illustrations for a third exemplary embodiment of a rail carriage group according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows, by way of example and in schematized form, a crane 3 in the form of a gantry crane which can move on two rails 2 in a rectilinear rail section and also around a curve, only partially illustrated. At each corner, the crane 3 or gantry crane has a rail carriage group 1. Each rail carriage group 1 has a plurality of running wheels 4 with which it can travel rectilinearly and around a curve on the rails 2. The running wheels 4 of each rail carriage group 1 run on precisely one rail 2. The rail carriage group 1 can be designed, for example, in each case as per the exemplary embodiments according to the invention that are described below.

The rail carriage groups 1 of this exemplary embodiment of a crane 3 are arranged in pairs and one behind another, as seen in the longitudinal direction of the rails 2, on an end carriage 20 of the crane 3. The end carriage 20 can also be referred to as a traveling gear carrier or chassis beam and constitutes the connection between the rail carriage group 1 and the superstructure, which is mounted thereon, of the crane 3. In the exemplary embodiment shown, four vertical supports 19 which bear two main girders 18 are arranged on the end carriages 20. The vertical supports 19 do not absolutely have to run strictly vertically. At least one crane trolley which is known per se, but is not illustrated here and which bears the lifting device runs on the main girder 18. The crane trolley is moveable along the main girder 18. This is known per se and does not need to be illustrated separately.

FIG. 2 shows, in a schematically illustrated vertical section, a rail 2 which is located freely on the upper edge 25 of the terrain and therefore on the underlying surface 24. The rail foot 23 of said rail stands on the upper edge 25 of the terrain. The rail head 21 bears the running surface 22 of the rail 2, along which the running wheels 4 of the rail carriage groups 1 roll. The rail head 21 is delimited laterally by the side surfaces 12. The side surfaces 12 are those surfaces of the rail 2 or of the rail head 21 which are arranged outside the running surface 22 of the rail 2 and generally run vertically or at least approximately vertically, with reference to the operating position. They are generally formed on the rail head 21. The construction which is illustrated schematically in FIG. 2 is known per se and does not to be explained further.

FIG. 3 shows, in schematized form and by way of example, how a rail 2, likewise known per se in the prior art, can be fitted into the underlying surface 24 in such a manner that the running surface 22 of said rail lies at least approximately flat with the upper edge 25 of the terrain. This construction is selected if the rail 2 is not intended to protrude from the upper edge 25 of the terrain. This may be the case, for example, if the rail is fitted in the region of a traffic surface on which vehicles which are not rail-bound, such as trucks, passenger cars and the like, are also intended to travel. The construction of the rail 2 per se is the same as in FIG. 2. The substantial difference, for the embodiments below, between the construction according to FIG. 3 and the construction according to FIG. 2, resides in the fact that, in the manner fitted as per FIG. 3, the side surfaces 12 of the rail 2 and of the rail head 21 are no longer completely freely accessible. In the case of the fitting of the rail as per FIG. 3, the side surfaces 12 are only still accessible within the relatively flat channels 26.

The manner in which an underlying surface 24 has to be realized so that a rail 2 is stably anchored in the underlying surface, even in the event of correspondingly high loads, as are produced, for example, by a crane, is known per se and does not need to be explained. The illustration of the underlying surface 24 in FIGS. 2 and 3 and also FIGS. 6, 9 and 12, which are also described below, is correspondingly simplified.

First of all, those features of the rail carriage group 1 that are reproduced in all of the exemplary embodiments are described below with reference to FIGS. 4 and 5 and therefore to the first exemplary embodiment according to the invention of a rail carriage group 1. Only then will the specific differences between the three exemplary embodiments be discussed.

FIG. 4 shows the rail carriage group 1 in the region of a curve of the rail 2, in a perspective illustration. FIG. 5 shows the same situation in top view. According to the invention, the running wheels 4 which rest with the running surfaces 33 thereof on the running surface 22 of the rail 2 are in each case individually rotatable or pivotable about a running-wheel axis of rotation 7 which is in each case vertical in the operating position shown. Each running wheel 4 is assigned a dedicated subframe 5. Each of said subframes 5 is rotatable together with the running wheel 4 about the running-wheel axis of rotation 7 which is vertical in the operating position. In all of the exemplary embodiments shown, provision is made for in each case two of the running wheels 4 with the subframes 5 assigned thereto to be rotatable about a common-running wheel axis of rotation 7 which is vertical in the operating position. The running-wheel rotational axes 8 of the running wheels 4 and the respective running-wheel axes of rotation 7 thereof are arranged skew. This means that they neither intersect nor run parallel to each other. The rotatability of the running wheels 4 and subframes 5 in each case in pairs about a common vertical running-wheel axis of rotation 7 permits the number of rotary joints 34 required to permit the rotatability about the vertical running-wheel axes of rotation 7 to be reduced. Suitable rotary joints 34 for this purpose are known per se in the prior art and do not have to be explained further.

For the sake of completeness, it is pointed out that, of course, there can also be exemplary embodiments of the invention in which the running wheels 4, and preferably also the subframes 5 thereof, are rotatable individually about vertical running-wheel axes of rotation 7 by each running wheel 4 being assigned a dedicated or separate running-wheel axis of rotation 7. However, this has the advantage of requiring more rotary joints 34 in order to realize the running-wheel axes of rotation 7.

In all of the exemplary embodiments shown here, it is provided for the running wheels 4 of the respective rail carriage group 1 jointly to transmit the entire load, which, in the operating position, emanates in the vertical direction 9 from the rail carriage group 1 itself and rests on the rail carriage group 1, to the rail 2. In short, the running wheels 4 are therefore the sole components of the rail carriage group 1 that are provided for transmitting the load to the rail 2.

In the exemplary embodiments shown, each rail carriage group 1 has six running wheels 4 and accordingly six subframes 5, which are in each case assigned in pairs to a running-wheel axis of rotation 7. The subframes 5 support the substructure 6 and also the motors 31 which are used to rotate the running wheels 4 about the running-wheel rotational axes 8 thereof for movement along the rail 2.

Generally speaking, the superstructure 6 of the rail carriage group 1 comprises all of those components of the rail carriage group 1 that are supported by the subframes 5. These components forming the superstructure 6 are generally at least mostly located above the subframe 5 in the operating position. In the exemplary embodiments shown, the superstructure 6 of the rail carriage group 1 comprises a girder in the form of the balancer 29 which is supported by in each case four running wheels 4 together with the four subframes 5 thereof. A rocker 28 of the superstructure 6 is supported on the balancer 29. This rocker 28 is supported at the other end thereof on two running wheels 4 and two subframes 5. The horizontal joints 36 are used for distributing load as uniformly as possible to the wheels 4 and are known per se. Between the balancer 29 and the rocker 28, and between the rocker 28 and the end carriage 20, joints, as known, for example, from EP 1 911 716 B1, are realized by means of the links 30 and the pivots 27. For the description of said joints, reference is explicitly made to the document mentioned, the content of which is therefore incorporated as part of the disclosure herein. Further joints which permit rotation about further vertical axes of rotation 32 are thereby provided at any rate between the balancer 29 and the rocker 28 and between the rocker 28 and the end carriage 20.

Following these general explanations, which also apply to the other exemplary embodiments according to FIGS. 7 to 12, the special characteristics of the first exemplary embodiment according to FIGS. 4 to 6 will now be specifically discussed. As also in the other exemplary embodiments, said special characteristics reside especially in the way in which the running wheels 4 together with the subframes 5 thereof are rotated or pivoted about the running-wheel axes of rotation 7, which are in each case vertical, in order optimally to follow the profile of the rail 2 in a straight line and in a curve. For this purpose, in the first and in the second exemplary embodiment, the side surfaces 12 of the rail 2 and of the rail head 21 are used as guide surfaces in order to align the respective running wheel 4 together with the subframe 5 with the rail 2 by rotating or pivoting about the running-wheel axis of rotation 7 running vertically.

For this purpose, in the first exemplary embodiment according to FIGS. 4 to 6, provision is made for at least one of the running wheels 4, preferably each running wheel 4, to be assigned at least one guide roller 17 which is rotatable about a guide-roller rotational axis 16, which is vertical in the operating position, for rotating the running wheel 4 about the running-wheel axis of rotation 7 by means of contact of the guide roller 17 with a side surface 12 of the rail 2. The guide rollers 17 here are advantageously fastened or mounted with their guide-roller rotational axes 16 thereof on the respective subframe 5. The guide-roller rotational axes 16 about which the guide rollers 17 rotate when running along the side surface 12 of the rail 2 are oriented vertically, as can be seen particularly readily in the sectional illustration according to FIG. 6.

FIG. 6 shows a vertical section orthogonally with respect to the longitudinal extent of the rail 2. The section plane here runs through the guide-roller rotational axes 16 of the guide roller 17. The running wheel 4 running with the running surface 33 thereof along the running surface 22 of the rail 2 is no longer illustrated sectioned in FIG. 6, since said running wheel is located behind the section plane. Preferred exemplary embodiments, such as the one shown here, make provision for each subframe to be assigned at least two guide rollers 17 which are arranged in pairs on mutually opposite sides of the rail head 21. Provision is particularly preferably made for at least some subframes 5 to be assigned four guide rollers 17. The latter can be located in pairs on mutually opposite sides of the rail head 21 and in front of and behind the running wheel 4 of the subframe 5. In the arrangement as realized here, in which two running wheels 4 with the two subframes 5 thereof are assigned to a common running-wheel axis of rotation 7, particularly preferred embodiments make provision for said two running wheels 4 and subframes 5 to be assigned a total of six guide rollers 17. Two of said guide rollers 17 are arranged in the region in front of the one running wheel 4, two guide rollers 17 are arranged in the region between the running wheels 4 and two guide rollers 17 are arranged in the region behind the rear running wheel 4. By this means, the number of guide rollers 17 that are required can be reduced. For illustrative purposes, the running-wheel rotational axis 8, which is located outside the section plane and behind the section plane, and the running-wheel axis of rotation 7 which runs vertically are also shown in FIG. 6, as is the vertical direction 9.

An advantage of the first exemplary embodiment according to FIGS. 4 to 6 resides in the fact that a dedicated drive is not required for rotating or pivoting the running wheels 4 and the subframes 5 about the vertical running-wheel axes of rotation 7, since the optimum alignment of the running wheels 4 for rectilinear travel and for traveling around a curve along the rail 2 is achieved by the guide rollers 17 interacting with the side surfaces 12 of the rail head 21.

However, it should also be pointed out that this type of rail carriage group 1 according to the invention, as is illustrated by way of example in FIGS. 4 to 6, can be used only if the rail 2 protrudes out of the underlying surface 24 to such an extent that the side surfaces 12 of the rail head 21 protrude over the upper edge 25 of the terrain to such an extent that the guide rollers 17 have an appropriate amount of space.

The second exemplary embodiment according to FIGS. 7 to 9 likewise involves an alternative according to the invention, in which the rotation of the running wheels 4 together with the subframe 5 about the vertical running-wheel axes of rotation 7 is realized by guidance on the rail 2 and on the side surfaces 12 thereof. Instead of the guide rollers 17 of the first exemplary embodiment, in the second exemplary embodiment according to FIGS. 7 to 9 the subframes 5 have flanged guide wheels 14 which run with the running surfaces 35 thereof on the running surface 22 of the rail 2 and are guided by means of the flanges 15 thereof by the side surfaces 12 of the rail 2. Generally speaking, in the case of this type of rail carriage group 1 according to the invention, provision is made for at least one of the running wheels 4, preferably each running wheel 4, to be assigned at least one flanged guide wheel 14 which is rotatable about a guide-wheel rotational axis 16, which is horizontal in the operating position, and has at least one flange 15 for rotating the running wheel 4 about the running-wheel axis of rotation 7 by means of contact of the flange 15 of the flanged guide wheel 14 with at least one side surface 12 of the rail 2. The flanged guide wheels 14 can have flanges 15 on one side or else on both sides and can correspondingly bear on one side or on both sides against the side surfaces 12 of the rail 2. The advantage of the alternative according to FIGS. 7 to 9 over the first exemplary embodiments resides in the fact that the rail 2 can also be recessed in the underlying surface 24, as illustrated in FIG. 9. FIG. 9 shows a vertical section through the rail 2 and through a flanged guide wheel 14, which runs thereon, in the region of the horizontal guide-wheel rotational axis 13. The flanges 15 which are arranged here on both sides of the flanged guide wheel 14 can readily be seen in FIG. 9, said flanges, in interaction with the side surfaces 12 of the rail 2, providing guidance along the rail 2 such that the running wheel 4, which is also shown behind the section plane in FIG. 9, together with the subframe 5 is always brought into the optimum angular position by rotation about the vertical running-wheel axis of rotation 7. By this means, as in the first exemplary embodiment, low-wear rectilinear travel and low-wear travel around a curve on the rail 2 are possible. The running wheels 4 of the two first exemplary embodiments do not have any flanges.

In particularly preferred embodiments of these exemplary embodiments, the flanged guide wheel 14 is suspended in a load-free manner. In this exemplary embodiment 2, the load which rests on the rail carriage group 1 and arises because of the rail carriage group 1 itself is transmitted to the rails 2 virtually exclusively via the running wheels 4. A correspondingly load-relieved or load-free suspension of the flanged guide wheels 14 can be achieved, for example, by the guide-wheel rotational axes 13 being supported on the subframe 5 only in the horizontal direction, but not in the vertical direction.

In the third exemplary embodiment, the running wheels 4 themselves each have flanges 11. However, because of the load which is transmitted to the rail 2 by the running wheels 4, this does not suffice by itself for the running wheels 4 to be rotated about the vertical running-wheel axes of rotation 7 in a manner following the rail 2 during travel around the curve and during rectilinear travel and during the transition in-between. In order to be able to rotate or pivot the running wheels 4 together with the subframes 5 in each case about the running-wheel axes of rotation 7 thereof, in each case two adjacent subframes 5 are connected here by means of a motorized drive 10 which actively brings about a corresponding rotation of the subframes 5 about the running-wheel axis of rotation 7. Generally speaking, in this type of exemplary embodiment, provision is made for at least one of the running wheels 4, preferably each running wheel 4, to be assigned a motorized drive 10 for rotating the running wheel 4 about the running-wheel axis of rotation 7. The term motorized drive 10 should be understood in general terms here. For example, it may involve drives which are motorized by means of an electric motor, hydraulics, pneumatics, etc. A common feature of all of these exemplary embodiments is that the profile of the rail 2 no longer leads to rotation of the running wheels 4 and subframes 5 about the vertical running-wheel axes of rotation 7 via guide bodies attached to the subframe 5, but rather said rotations are realized actively by a dedicated motorized drive 10. Of course, provision may be made for each running wheel 4 or each subframe 5 to be assigned a dedicated, corresponding, motorized drive 10. However, provision may also be made, as in the exemplary embodiment according to FIGS. 10 to 12, for a motorized drive 10 to be used for rotating two or more subframes 5.

FIG. 12 in turn shows a vertical section through a rail 2 which is recessed in the underlying surface 24 and has a running wheel 4 running thereon. In this alternative, as can be readily be seen in FIG. 12, provision is made, generally speaking, for the running wheel 4, preferably all of the running wheels 4, to have at least one flange 11 for guiding the, preferably respective, running wheel 4 on at least one side surface 12 of the rail 2. In the exemplary embodiment specifically realized, the running wheel 4 has two flanges 11. If, in this exemplary embodiment, the motorized drives 10 were not realized, then at least very high frictional forces would occur on the running wheels 4 at the flanges 11 thereof when traveling around a curve, the frictional forces sooner or later resulting in rapid wear on the running wheels 4, in particular on the flanges 11 thereof and also on the rail 2.

For the sake of completeness, it is also emphasized that the invention is, of course, not limited to the exemplary embodiments shown. In particular, the number of subframes 5 and running wheels 4 and the embodiments of the superstructure 6 can vary greatly. In particular, the various alternatives of the exemplary embodiments can also be combined with one another, where expedient.

Key to the reference numbers: 1 Rail carriage group 19 Vertical supports 2 Rail 20 End carriage 3 Crane 21 Rail head 4 Running wheel 22 Running surface 5 Subframe 23 Rail foot 6 Superstructure 24 Underlying surface 7 Running-wheel axis of rotation 25 Upper edge of the terrain 8 Running-wheel rotational axis 26 Channel 9 Vertical direction 27 Pivot 10 Motorized drive 28 Rocker 11 Flange 29 Balancer 12 Side surface 30 Link 13 Guide-wheel rotational axis 31 Motor 14 Flanged guide wheel 32 Further axis of rotation 15 Flange 33 Running surface 16 Guide-roller rotational axis 34 Rotary joint 17 Guide roller 35 Running surface 18 Main girder 36 Horizontal joint 

1. A rail carriage group for a crane which is moveable on rails with a rectilinear rail profile and around at least one curve and in a transition between the rectilinear rail profile and the curve, comprising at least two running wheels that support subframes of the rail carriage group, and the subframes support a superstructure of the rail carriage group, at least one of the running wheels is rotatable individually about a running-wheel axis of rotation which is vertical in an operating position.
 2. The rail carriage group as claimed in claim 1, wherein at least one of the running wheels is assigned a dedicated subframe, and the subframe is rotatable together with the running wheel about the running-wheel axis of rotation which is vertical in the operating position.
 3. The rail carriage group as claimed in claim 1, wherein in each case two of the running wheels or two of the subframes are rotatable about a common running-wheel axis of rotation which is vertical in the operating position.
 4. The rail carriage group as claimed in claim 1, wherein the running wheels for rolling along the rail are in each case rotatable about a running-wheel rotational axis which is horizontal in the operating position, and the running-wheel rotational axis of the running wheel and the running-wheel axis of rotation of the running wheel are arranged skew with respect to each other.
 5. The rail carriage group as claimed in claim 1, wherein the running wheels of the rail carriage group jointly transmit an entire load, which, in the operating position, emanates in the vertical direction from the rail carriage group itself and are transmitted from the rail carriage group to the rail.
 6. The rail carriage group as claimed in claim 1, wherein at least one of the running wheels is assigned at least one guide roller which is rotatable about a guide-roller rotational axis, which is vertical in the operating position, for rotating the running wheel about the running-wheel axis of rotation by contact of the guide roller with at least one side surface of the rail.
 7. The rail carriage group as claimed in claim 1, wherein at least one of the running wheels is assigned at least one flanged guide wheel which is rotatable about a guide-wheel rotational axis, which is horizontal in the operating position, and the at least one flanged guide wheel has at least one flange for rotating the running wheel about the running-wheel axis of rotation by contact of the flange of the flanged guide wheel with at least one side surface of the rail.
 8. The rail carriage group as claimed in claim 1, wherein at least one of the running wheels is assigned a motorized drive for rotating the running wheel about the running-wheel axis of rotation.
 9. The rail carriage group as claimed in claim 8, wherein the running wheel has at least one flange.
 10. A crane comprising at least one of the rail carriage groups as claimed in claim
 1. 11. The rail carriage group as claimed in claim 1, wherein there are at least four of the running wheels.
 12. The rail carriage group as claimed in claim 1, wherein each of the running wheels is rotatable individually about a respective running-wheel axis of rotation which is vertical in an operating position. 